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Number of modes in optical fiber

  1. Apr 29, 2017 #1
    1. The problem statement, all variables and given/known data
    Can a single mode fiber become multimode if the wavelength of the light passed through it is small enough?

    I put a HeNe laser (633nm) through what I thought was a single mode fiber. If it's supposed to operate at 1300nm, then would a low wavelength of 633nm cause multiple modes in the single mode fiber?

    2. Relevant equations
    number of modes = operational wavelength / wavelength used

    3. The attempt at a solution
    number of modes = 1300nm/633nm = (approx.) 2 modes?

    I'm not sure why my image isn't showing a uniform mode / pattern.

    Attached Files:

  2. jcsd
  3. Apr 29, 2017 #2


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    Gold Member

    Maybe you have a multimode fibre?
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